Method for making a finally shaped forming tool and forming tool made by same

ABSTRACT

The forming tool has a structured forming surface having a high surface quality and uniform structure so that it accurately produces a predetermined structure in substrate. To avoid the great expense and effort associated with final shaping of the forming tools from blocks or rounded bodies made by forging or by a HIP method with subsequent machining, first a glass or plastic mold ( 1 ) is made with a molding surface for forming the structured forming surface of the forming tool, which is the negative of the structured forming surface for the forming tool with predetermined dimensions and surface quality in accordance with specifications of the structured forming surface of the forming tool; then the molding surface is coated with at least one coating material selected specifically according to the specifications to form a cladding body ( 2 ) in the glass or plastic mold, next the cladding body ( 2 ) with the structured forming surface is released from the glass or plastic mold ( 1 ) and bonded to a base body with a non-structured surface of the cladding body ( 2 ) in contact with the base body to form the forming tool with the structured forming surface.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of making a finallyshaped forming tool with a forming surface, which is preferablystructured and has a highly uniform structure. The invention alsorelates to a finally shaped forming tool with a forming surface that ispreferably structured and that has a highly uniform structure.

[0003] 2. Related Art

[0004] Forming tools, typically with predetermined structures on theirsurfaces, are required to form or shape glass or plastic in aplasticized state. The predetermined structures in the surfaces of theseforming tools are the negative of the structures produced in the glassor plastic. These forming tools are typically dies or roller shapedtools. The structures to be produced can be in the μm range, e.g. as inthe hot forming of so-called channel plates for flat screen displays ofmodern TV sets.

[0005] Currently casting methods are used to obtain the finally shapedforming tool. The structural uniformity obtained with these castingmethods is limited by technical considerations. There are strictrequirements for forming tools in certain different manufacturingprocesses, e.g. in the hot forming of glass substrates regardingstructural uniformity as well as chemical composition. Structuralnon-uniformities, which can arise because of casting conditions, e.g.pores, holes, grain size variations, texture variations, mounds orprotruding accumulations, can be disadvantageously copied into thesubstrate during the forming process with the forming tool.

[0006] Forming tools are thus typically forged with high structuraluniformity since clearly more uniform forming thereby results.

[0007] Another process for guaranteeing high structural uniformitycomprises making blocks by a HIP method. Materials are encapsulated andsealed in a vacuum-tight manner in a sheet structure in the HIPprocess(hot-isostatic-press). Subsequently the base block for theforming tool arises because of the applied high pressure andtemperature. The combination “solid-powder” is an example of a possiblematerial combination. That means that a supporting material is processedinto a desired form (shape) and after that a capsule with an internalchamber is provided over the resulting body. The interior chamber isfilled with powder after that. In the HIP process then the powder issintered together and combines with the supporting material forming adiffusion zone.

[0008] An extremely high quality surface structure is obtained in theHIP process based on small powder grain size up to the nm size and onthe sintering without melt phase.

[0009] The disadvantage of both these manufacturing methods is that inorder to obtain a high degree of structural uniformity final shapingfrom initially prepared blocks and/or rounded blanks must be performeddisadvantageously mechanically. This is very expensive, particularly forwear and corrosion-resistant materials, such ceramics, high temperaturealloys. Also structures in the μm-range cannot be made economically onthese tool surfaces.

SUMMARY OF THE INVENTION

[0010] It is an object of the present invention to conduct the processesof the above-described type so that the finally shaped forming tools arebetter than those of the prior art, both in regard to their geometricform (contour) and also the surface quality, including their roughnessand structure, and also so that they have higher surface uniformity withdistinctly reduced processing work.

[0011] This object is attained by a process of the above-described kindfor making finally shaped forming tools with the structured formingsurfaces with a high surface uniformity comprising the following steps:

[0012] a) making a glass or plastic mold having a molding surface forthe finally shaped forming tool that is formed as the negative of thestructured forming surface for the forming tool with predetermineddimensions with a surface quality, as required by the forming surface ofthe forming tool;

[0013] b) coating the molding surface of the glass or plastic mold withat least one material selected specifically according to the structuredforming surface of the forming tool so as to form a cladding body in theglass or plastic mold, the cladding body being provided with thestructured forming surface of the forming tool,

[0014] c) releasing the cladding body with the structured formingsurface from the glass or plastic mold; and

[0015] d) bonding the cladding body to a base body with a non-structuredsurface thereof in contact with the base body to form the finally shapedforming tool with the forming surface.

[0016] A finally shaped forming tool according to the invention can bemanufactured comparatively economically both with the required geometricshape and surface quality, especially the surface roughness andstructuring. At the same time uniform structural properties areobtained.

[0017] These methods can produce layered systems or material gradientsand three dimensional structures in the μm-range on the working surfacesbesides processing an exceptionally large number of materialcompositions, including metallic materials and also ceramic materials.

[0018] These advantages are present, particularly when thermal sprayingtechnology is used to provide the negative coating on the negative mold.Other coating technologies can also be utilized.

[0019] According to various embodiments of the method according to theinvention the negative mold is a plastic body structured by means oflithography methods.

[0020] In other embodiments mechanical methods or methods based onthermal principles are used to structure the negative mold.

[0021] The thermal spraying occurs according to a first embodiment ofthe invention preferably by flame spraying methods, especially by a HVOFmethod. This method permits a layer structure with a high structuraluniformity.

[0022] A second embodiment of the process according to the invention, inwhich the thermal spraying comprises plasma spraying, also provides thislatter advantage. The preferred plasma spraying method is a VPS or LPPSmethod. These methods have the additional advantage that a wide range ofmaterials, especially hard alloys and hard materials, such as carbides,can be sprayed.

[0023] The foregoing methods permit the spraying of both single-phasematerials and also material combinations, in order to form layeredsystems or material gradients. Thus in the method according to theinvention the materials for the structured forming surface of theforming tool can be adjusted in a simple way.

[0024] The above-described methods permit a predetermined coatingthickness to be applied to the negative mold. This coating thickness isselected so that the coating body released from the negative mold can bebonded with the supporting material or body of the forming tool.

[0025] When the coating thickness according to a first embodiment isfrom 100 μm to 5 mm, the manufacture of the forming body is performed,preferably so that the coating or cladding body released from thenegative mold is bonded with another material as part of a HIP capsuleby an HIP method to make the forming tool. These methods guarantee apermanent intimate material bond between the separately made structuredcoating or cladding body and the base or supporting material of theforming tool.

[0026] When the coating thickness is sufficiently large, up to 20 mm,the cladding body can be used directly to provide the forming surface ofthe forming tool, since the cladding body released from the negativemold can be combined mechanically with a based body to form the formingtool.

[0027] A first layer made by thermal spraying can be reinforced or builtup by bonding to a large layer thickness, which speeds up the making ofthick coatings.

[0028] In regard to the finally shaped forming tool with the structuredforming surface of high structural uniformity the above-describedobjects of the invention are attained by a structured forming surface,which is formed by a separately produced coating body or cladding bodymade by thermal spraying, which is bonded with supporting material toform the forming tool.

[0029] The forming tool should be structured so that the separatelyproduced coating body has a thickness of up to 20 mm and is mechanicallybonded with the supporting material, or so that the separately producedcladding body has a thickness of from 500 μm to 5 mm and is a part of aHIP capsule, which is bonded, connected or attached by means of an HIPmethod with the base material.

BRIEF DESCRIPTION OF THE DRAWING

[0030] The objects, features and advantages of the invention will now beillustrated in more detail with the aid of the following description ofthe preferred embodiments, with reference to the accompanying figures inwhich:

[0031]FIG. 1 is a schematic longitudinal cross-sectional view through amold acting as a pattern for the later-formed forming tool, in which thenegative of the structure of the later-formed forming tool isincorporated,

[0032]FIG. 2 is a schematic longitudinal cross-sectional viewillustrating the step of making a coating or cladding body in the moldshown in FIG. 1 with a given material by thermal spraying methods,

[0033]FIG. 3 is a schematic longitudinal cross-sectional view showingthe mechanical attachment of the cladding body released from the moldwith a based body to form a forming tool, and

[0034]FIG. 4 is a schematic longitudinal cross-sectional view showingthe bonding of the cladding body or coating released from the mold in aHIP capsule by means of a HIP process with a base and/or supportingmaterial to form the forming tool.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] A preferred embodiment of the method for making a finally shapedforming tool with a structured forming surface, which guarantees a veryhigh uniformity of the surface structure, is illustrated in the drawing.

[0036] In a first step shown in FIG. 1 a mold 1 is provided having apattern for forming the forming tool with the structured surface, i.e.the mold 1 has a negative shape corresponding to the structured surfaceof the forming tool to be made. In order to simplify the illustration ofthe mold and the corresponding forming body the mold is shown with onlya comparatively simple surface structure including a straight section 1a and two curved sections 1 b separated from the straight section 1 a bytwo cavities 1 c.

[0037] In the case of actual embodiments of the forming tool thenegative structure of the mold is worked according to the surfacestructure of the forming tool to be made. The dimensions of the negativestructure in the mold must be guided by dimensions, which depend on theforming process performed with the later-formed forming tool. In thehot-forming the dimensions of the surface structure of the forming toolchange, for example, because of the unavoidable thermal expansionoccurring during the hot-forming process, which must be taken intoconsideration in selection of the dimensions for the negative structureof the mold according to FIG. 1.

[0038] The making of the negative mold 1 can occur in different ways.One way is the so-called prototyping. In this method the negative moldwith the desired geometric contour/structure is made by means oflithography methods (mask engineering in connection with photo lacquer)from a plastic body and the required surface quality is guaranteed.These lithography methods are basically known and need not be explainedin further detail.

[0039] Another method for making the forming tool consists in grinding,sandblasting, machining or structuring with methods that operate bythermal action principles, such as erosion or laser machining so that abase body is provided with the negative structure of the forming tool.

[0040] In the following process step shown in FIG. 2 the negative mold1, preferably coated by means of thermal spraying technology, isprovided with a coating 2 of a predetermined thickness as indicated bythe arrows in FIG. 2.

[0041] Thermal spraying methods include flame spraying, electric arcspraying, plasma spraying and special spraying methods, such asdetonation coating and condensation spraying. These methods are alsoknown basically and do not need to be explained further herein. Theplasma spraying is particularly significant for the present application,because of the high quality of the coating formed by it, especially inregard to uniformity, and because the method permits the processing ofhigh melting metallic and ceramic materials, which are required in thestructuring of glass on account of the required heat and corrosionresistance. Alloys of nickel/chromium, cobalt-based alloys and carbidesare included in these materials.

[0042] The so-called HVOF method (high velocity oxide fuel flamespraying) in flame spraying and the so-called VPS method (vacuum plasmaspraying) or the LPPS method (low pressure plasma spraying) in plasmaspraying have special significance. Surfaces having very slight porosityand high uniformity are obtained immediately in these processes.

[0043] The effectiveness of the process of thermal spraying depends in aknown way decisively on the parameters of the process during coating,here of the negative mold 1. Those parameters are, for example, thecarrier gas supply, the spacing of the burner nozzle from the negativemold, the temperature, etc. These parameters are varied according to thematerial to be sprayed and the desired geometry of the negative mold.They are determined in the case of particular embodiments by one skilledin the art.

[0044] A coating 2 made from a predetermined material with apredetermined thickness is provided on the negative mold 1 at the end ofthe thermal spraying step, which has the desired finally shapedstructure in regard to geometry and surface quality with the highstructural uniformity on the contacting surface of the negative mold.

[0045] This coating 2 is removed from the negative mold 1 to make theforming tool. The release of the coating 2 can be made easy by suitablepre-treatment of the surface of the negative mold 1 to be coated priorto the coating.

[0046] The released coating 2 can then be processed in different waysfor forming the surface structure of the forming tool.

[0047] According to a first possibility the coating can be formed sothick, about 1 to 20 mm, that the outer shape of the outer layer of theforming tool is obtained as a coating or cladding body. After releasefrom the mold 1 this cladding body, as shown in FIG. 3, can be clampedon the base body 3 for the forming tool, e.g. by a suitable die, inorder to provide a mechanically stable forming tool.

[0048] According to another possibility a coating 2 with a thickness ofabout 1 to 5 mm is produced. This coating is released from the negativemold, as shown in FIG. 4, to form a part of an HIP capsule 4, which isfilled with a powder for pressing, if necessary in connection with anembedded solid material or body. The thickness of the coating body 2forming the part of the HIP capsule should be larger than, for exampleat least twice as large as, that of the remaining capsule half. Theshrinking or changing of the surface can be prevented because of thatfeature. Only the edges are warped or twisted by the HIP process.

[0049] A working device forming the forming tool is available in whichthe coating body 2 provides a structuring surface, which comes intoworking contact, e.g., with the glass or plastic substrate and which hasthe negative of the structure to be formed on its surface afterperforming the above-described HIP method, alternatively also after abonding process. The negative structuring surface of the forming toolcomprises a straight section 2 a, the two curved sections 2 b and theraised structures 2 c.

[0050] Instead of the coating consisting of only a single layer ofmaterial the coating 2 can be made up of several layers of differentmaterials applied one over the other. Also several materials can besimultaneously sprayed to form the coating.

[0051] Preferably the sprayed coating body is sealed by a subsequent HIPprocess.

[0052] The disclosure in German Patent Application 100 34 508.5-16 ofJul. 15, 2000 is incorporated here by reference. This German PatentApplication describes the invention described hereinabove and claimed inthe claims appended hereinbelow and provides the basis for a claim ofpriority for the instant invention under 35 U.S.C. 119.

[0053] The wording “surface corresponding to the negative of thestructure to be provided in the glass or plastic substrate” means simplythat the surface is shaped or structured so as to produce the articlefrom the glass or plastic substrate with a desired or predeterminedshape.

[0054] The term “negative mold” for the forming tool means that the moldis shaped with a surface contacting the forming tool during the moldingwhich is the negative of the surface formed on the forming tool, i.e.the mold is shaped to produce the desired predetermined surface on theforming tool. Of course during the molding this means that there are nogaps or spaces between the structuring surface on the forming tool andthe contacting surface of the mold. This is the usual situation for amold and an article molded by means of the mold.

[0055] While the invention has been illustrated and described asembodied in an end-contoured shaping forming tool with a forming surfaceand method of forming same, it is not intended to be limited to thedetails shown, since various modifications and changes may be madewithout departing in any way from the spirit of the present invention.

[0056] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic or specific aspects of thisinvention.

[0057] What is claimed is new and is set forth in the following appendedclaims.

We claim:
 1. A method for making a finally shaped forming tool with astructured forming surfaces having a uniform surface structure, saidmethod comprising the following steps: a) making a glass or plastic mold(1) having a molding surface for forming the structured forming surfaceof the forming tool, said molding surface being a negative of thestructured forming surface for the forming tool with predetermineddimensions and a surface quality in accordance with specifications ofthe structured forming surface of the forming tool; b) coating themolding surface of the glass or plastic mold (1) with at least onematerial selected specifically according to said specifications for thestructured forming surface of the forming tool so as to form a claddingbody (2) in the glass or plastic mold, the cladding body being providedwith the structured forming surface of the forming tool, c) releasingthe cladding body (2) with the structured forming surface from the glassor plastic mold (1); and d) bonding the cladding body to a base bodywith a non-structured surface of the cladding body (2) in contact withthe base body to form the finally shaped forming tool with thestructured forming surface.
 2. The method as defined in claim 1, furthercomprising making said mold by structuring a plastic body by means of alithographic method
 3. The method as defined in claim 1, furthercomprising making said mold by structuring a glass or plastic body bymeans of a mechanical process.
 4. The method as defined in claim 1,further comprising making said mold by structuring a glass or plasticbody by means of a thermal method.
 5. The method as defined in claim 1,wherein the coating of the molding surface of said mold occurs by meansof a thermal spraying method.
 6. The method as defined in claim 5,wherein said thermal spraying method comprises a flame spraying method.7. The method as defined in claim 6, wherein said flame spraying methodcomprises a high velocity oxide fuel flame spraying method.
 8. Themethod as defined in claim 5, wherein said thermal spraying methodcomprises a plasma spraying method.
 9. The method as defined in claim 8,wherein said plasma spraying method comprises a vacuum plasma sprayingor low pressure plasma spraying method.
 10. The method as defined inclaim 1, wherein said coating of the molding surface of the glass orplastic mold comprises spraying a single phase material on the moldingsurface.
 11. The method as defined in claim 1, wherein said coating ofthe molding surface of the glass or plastic mold comprises spraying amaterial combination in a layered structure or to provide a materialgradient.
 12. The method as defined in claim 1, wherein the coating ofthe molding surface of the mold takes place to provide a coatingthickness of from 100 μm to 5 mm.
 13. The method as defined in claim 1,wherein the coating of the molding surface of the mold takes place toprovide a coating thickness of up to 20 mm.
 14. The method as defined inclaim 13, wherein the coating of the molding surface takes place by athermal spraying method to form a coating member and further comprisingreinforcing or building up said coating member by a bonding process. 15.The method as defined in claim 1, wherein said cladding body (2)released from said mold (1) is combined with said base body (3) bymechanical means to form said forming tool.
 16. The method as defined inclaim 1, wherein said cladding body (2) released from said mold (1) iscombined as a part of a hot-isostatic-press capsule with anothermaterial by means of a hot-isostatic-press process to form the formingtool.
 17. A finally shaped forming tool with a forming surface, saidforming tool comprising a base or supporting body (3; 4; 5) and acladding body (2) bonded to the base or supporting body, said claddingbody (2) being separately formed from said base or supporting body withsaid forming surface.
 18. The finally shaped forming tool as defined inclaim 17, wherein said forming surface is uniformly structured.
 19. Thefinally shaped forming tool as defined in claim 17, wherein saidcladding body (2) has a thickness of up to 20 mm and is mechanicallybonded with the base or supporting body.
 20. The finally shaped formingtool as defined in claim 17, wherein cladding body (2) has a thicknessof from 100 μm to 5 mm and is part of a hot-isostatic-press capsule andis combined with another material by means of a hot-isostatic-pressprocess or by bonding to form the forming tool.
 21. The finally shapedforming tool as defined in claim 15, wherein the cladding body is formedby a method comprising thermal spraying.